RAM (Random Access Memory)
Definition
RAM is a type of fast, volatile memory used by the computer to store data and instructions that are actively being used or processed. Its volatility means that all data is lost when the power is turned off.
Key Point
RAM Characteristics:
• Volatile - data lost when power removed
• Very fast read/write access
• Stores currently running programs and active data
• Acts as working memory for the CPU
• More RAM allows more applications to run simultaneously
• Measured in GB (commonly 8GB, 16GB, 32GB)
• Volatile - data lost when power removed
• Very fast read/write access
• Stores currently running programs and active data
• Acts as working memory for the CPU
• More RAM allows more applications to run simultaneously
• Measured in GB (commonly 8GB, 16GB, 32GB)
ROM (Read-Only Memory)
Definition
ROM is non-volatile memory that holds data that does not change, such as the computer's startup instructions. Unlike RAM, the data in ROM remains intact even when the computer is powered off.
Key Point
ROM Characteristics:
• Non-volatile - data persists without power
• Read-only during normal operation (can be programmed specially)
• Contains firmware and boot processes (BIOS/UEFI)
• Stores permanent system instructions
• Slower than RAM
• Cannot be used as working memory
• Non-volatile - data persists without power
• Read-only during normal operation (can be programmed specially)
• Contains firmware and boot processes (BIOS/UEFI)
• Stores permanent system instructions
• Slower than RAM
• Cannot be used as working memory
RAM vs ROM Comparison
Key Point
Volatility
• RAM: Volatile (data lost without power)
• ROM: Non-volatile (data persists)
Read/Write
• RAM: Read and write frequently
• ROM: Primarily read-only
Speed
• RAM: Very fast
• ROM: Slower
Purpose
• RAM: Working memory, running programs
• ROM: Permanent instructions, firmware
Upgradeable
• RAM: Yes - can add more RAM
• ROM: Usually soldered to motherboard
Contents
• RAM: Changes constantly
• ROM: Fixed (or rarely changed)
• RAM: Volatile (data lost without power)
• ROM: Non-volatile (data persists)
Read/Write
• RAM: Read and write frequently
• ROM: Primarily read-only
Speed
• RAM: Very fast
• ROM: Slower
Purpose
• RAM: Working memory, running programs
• ROM: Permanent instructions, firmware
Upgradeable
• RAM: Yes - can add more RAM
• ROM: Usually soldered to motherboard
Contents
• RAM: Changes constantly
• ROM: Fixed (or rarely changed)
ROM in Embedded Systems
In a desktop computer, ROM holds the start-up instructions (the BIOS). An embedded system, such as a washing machine or a digital photo frame, often holds its whole operating system or firmware in ROM.
Key Point
Why an embedded system stores its software in ROM:
• The software rarely or never needs to be updated
• It cannot be overwritten or deleted by accident
• It is not lost when the device is switched off, and is available as soon as the device is switched on
• The program does not have to be loaded from separate secondary storage, which saves time and keeps the device small
Any data the device saves is usually written to flash storage, which is small, durable and low in power use.
• The software rarely or never needs to be updated
• It cannot be overwritten or deleted by accident
• It is not lost when the device is switched off, and is available as soon as the device is switched on
• The program does not have to be loaded from separate secondary storage, which saves time and keeps the device small
Any data the device saves is usually written to flash storage, which is small, durable and low in power use.